The present invention relates generally to techniques for replacing equipment at a wellsite. More specifically, the invention relates to techniques for replacing wellsite equipment, for example, in applications relating to the field of blowout preventers (BOPS) and strippers, and to a device for remotely replacing subsea equipment, such as a worn packer element in a BOP or stripper, used for example in sub-sea applications.
Oilfield operations are typically performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites, and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Many oilfield operations occur in the sea, or ocean. Subsea oilfield operations typically require the wellhead and other wellsite equipment to be located on the seabed, while an oil platform, or vessel, may be located at the water's surface. The wellsite equipment located at the seabed may comprise such subsea equipment as blow out preventers (BOPs), strippers, control devices, supporting tubing injectors, tubing reels, wireline units, and the like. The stripper may act as a seal that the conveyance, such as coiled tubing, is run through. As the coiled tubing is fed through the stripper, the stripper may seal the outer surface of the coiled tubing, thereby preventing sea water from entering the well, and/or from wellbore fluids from leaving the wellbore inadvertently. The BOP may act as a safety device designed to ‘seal in’ large pressure surges in the wellbore. The BOP may have rams that automatically shut thereby closing and sealing in the wellbore.
Drilling and work-over operations with the well heads installed under water make it desirable to perform specific repair and maintenance evolutions without bringing the subsea equipment, such as a worn stripper element or an entire blowout preventer (BOP), to the surface. Known methods at depths below safe depths for diver operations require bringing the BOP components, and the stripper components to the surface for refurbishment. Such an operation is typically expensive, time consuming, and results in significant down time for the well being maintained.
In some cases, shallower equipment replacement operations may be performed by a diver. However, as drilling operations take place at ever increasing depths, such techniques become impractical. It is desirable to develop techniques, such as those provided in the following disclosure, to facilitate replacement of worn packer sealing elements, or seal assemblies, and/or replacement of such an element with a different size or having a different function, such as changing from a packer to a slip element. Further, these functions are preferably performed without the aid of a diver.
Attempts have been made to replace components of BOPs as described, for example, in U.S. Pat. Nos. 5,961,094 and 3,741,296. Techniques have also been provided for replacing packers in an undersea application as described, for example in U.S. Pat. Nos. 5,961,094; 6,012,528; and 6,113,061.
Despite the development of techniques for replacing packers and components of BOPs, there remains a need to provide advanced techniques for performing replacement operations. It may be desirable to provide techniques that provide for replacement of various subsea equipment, such as packers, seal assemblies, downhole tools, etc. It may be further desirable that such techniques be performed remotely and/or automatically. Preferably, such techniques involve one or more of the following, among others: efficient replacement, reduced downtime, simpler structure (for example to broaden the application for remotely changing a worn packer element), reduced manning, etc. The present invention is directed to fulfilling this need in the art.